Re: [PATCH v5 0/5] gpio: Add GPIO Aggregator

From: Eugeniu Rosca
Date: Tue Feb 18 2020 - 12:04:41 EST

Hi Geert,

On Tue, Feb 18, 2020 at 04:18:07PM +0100, Geert Uytterhoeven wrote:
> Hi all,
> GPIO controllers are exported to userspace using /dev/gpiochip*
> character devices. Access control to these devices is provided by
> standard UNIX file system permissions, on an all-or-nothing basis:
> either a GPIO controller is accessible for a user, or it is not.
> Currently no mechanism exists to control access to individual GPIOs.
> Hence this adds a GPIO driver to aggregate existing GPIOs, and expose
> them as a new gpiochip. This is useful for implementing access control,
> and assigning a set of GPIOs to a specific user. Furthermore, this
> simplifies and hardens exporting GPIOs to a virtual machine, as the VM
> can just grab the full GPIO controller, and no longer needs to care
> about which GPIOs to grab and which not, reducing the attack surface.
> Recently, other use cases have been discovered[1]:
> - Describing simple GPIO-operated devices in DT, and using the GPIO
> Aggregator as a generic GPIO driver for userspace, which is useful
> for industrial control.
> Changes compared to v4[2]:
> - Add Reviewed-by, Tested-by,
> - Fix inconsistent indentation in documentation.

I confirm that the diff between v4 and v5 comprises whitespace only.
Thanks for your time to develop this useful functionality!

Best Regards
Eugeniu Rosca